1. Field of the Invention
The invention relates to a guide bar drive in a knitting machine with a linear motor that has a stator and a rotor (moving coil) which can be moved in a translational manner in the stator in the longitudinal direction.
2. Discussion of Background Information
The guide bars or guide rails of a knitting machine have to be driven at least in the longitudinal direction for the loop formation of a textile knitted fabric. Furthermore, in a work cycle the guide bars are often also moved crosswise to the longitudinal direction, as a rule swiveled. Mechanical gearings were used in the past for the movement in the longitudinal direction. A typical gearing thereby features a cam plate that interacts with a push rod and moves the guide bar to and fro in a predetermined manner. However, only cam plates with a limited diameter, and thus with a limited circumference, can be used. The pattern repeat is thus limited. Moreover, a different cam plate is needed for each pattern. For a pattern change, the knitting machine has to be stopped and adapted.
For longer pattern repeats, pattern chains can also be used instead of the cam plates. However, the knitting machine has to be adapted for a pattern change here, too.
Servo-controlled linear gearings have therefore also been used. Linear gearings with servo motors which work in a rotary manner can be used only to a limited extent due to the space conditions in a knitting machine. The gearings, which serve as a converter of a rotary to a linear movement, are subject to wear and require a complex construction because as a rule an oil lubrication and accordingly a housing with an oil seal is necessary.
DE 42 17 357 C2 shows a guide bar drive of the type mentioned at the outset, namely a linear motor that can be connected to the guide rail of a warp knitting machine. The rotor can be moved to and fro in the stator. It is supported in linear guides with axial extensions that are attached on the end faces of the stator. Problems with respect to space requirements also arise with this solution. As long as the drive has to drive only one guide bar, there are no conflicts. However, when several guide bars are used, they have to be arranged as closely adjacent to one another as possible, so that the guides can be guided through needle gaps between needles if possible at the same time or with only a slight delay. If the guide bars are very close together, then accordingly only little space is available for the linear motor.